Copper's role in connective tissue is linked to the enzyme lysyl oxidase.
From a biochemical perspective, copper is a cofactor for the enzyme and a
determinant of its activity in connective tissues. Lysyl oxidase catalyses a
post-translational oxidation of certain lysine and hydroxylysine residues.
The peptidyl aldehydes so formed become active centres for the formation of
cross-links in collagen and elastin. Less well understood is how copper
controls the steady-state activity of lysyl oxidase; the enzyme fails in
copper deficiency. Giving copper to a deprived animal increases lysyl
oxidase activity in aortic tissue. Such activation in vivo appears to
require caeruloplasmin. Suspending aortic tissue in a copper-enriched growth
medium also activates lysyl oxidase provided that tissue structure is kept
intact. Activation in vitro occurs with the binding of copper to a
large-molecular-weight component, presumably the enzyme. Binding will not
occur if protein synthesis is blocked. These studies clearly show that the
synthesis of mature elastin and collagen can be controlled by the
availability of copper. They further suggest that transport of copper to
aortic tissue and its engagement to lysyl oxidase are linked to the
synthesis or lysyl oxidase, an extracellular carrier, or both.